Earth grounding requirements on industrial equipment

[kelec]

reference thread 242-99843

The question is related to the below Post :

You should carefully review definition of GEC (grounding electrode conductor). GEC and grounding electrode is not something you install at every 'equipment'.

GEC is the conductor used to ground the system's "grounded conductor" , such as neutral of 4 wire system, to the system’s grounding electrode, such as the building steel or a ground rod. Now this connection is typically made only at one point, which is the service entrance or the secondary of a transformer or in other words the origin of the system.

From that point onwards the "grounded conductor" (e.g. neutral) is not grounded again while a ECG (equipment grounded conductor) or the "green wire" is always installed with every branch circuit. (metal raceways are acceptable by Code as ECG, but let us not use it for the purpose of this discussion).

The only connection between the ECG and GEC is at the service entrance equipment or the secondary of a separately derived system.

Now if your 480V system is grounded at its origin and your machine does not require a neutral, you need not install the neutral but you install the ECG and "bond' all non-current carrying surfaces of the equipment (enclosure, frame, etc.) to the ECG. For extra safety you can "bond' such non-carrying surfaces to supplemental grounded surfaces such as building steel but not 'required' the code.

As for the grounding the static charges goes all you need is the all non- current carrying surfaces that a person can touch or span by standing at one location should be bonded together and eventually conncetded to a effectively grounded surface or a seprate grouding electrode and more importantly the "ground" chasis of the equipment generating static. If you are bringing your power feed with ECG (green wire) you should also connect that to this 'bonded' system. Now a seprate grounding electrode, if installed for this purpose is not your system grounding electrode but a supplemetnal grounding electrode

Question :

This post talks about not requiring to install a neutral if the machine does not require a neutral and installing the
ECG (480V system)

Is it the same situation for a 208V. I have a 3 phase 3 wire 208V equipment where i am not running a neutral to the equipment's disconnect.But as per 200.2 Article it says all premise wiring shall have grounded conductor.do i have to run a neutral to the equipment's disconnect. If not required can you please specify the code number where it says so.

 

[resqcapt19]

200.2 does not require that you run a grounded conductor with a feeder or branch circuit that does not use it. It only says that the system has to have a grounded conductor if it is required to be a grounded system. The only disconnet that you have to run a grounded conductor to, even if the circuit does not use it, is the service disconnect. 250.24(C)

 

[dpc]

I agree. But I would check the equipment requirements very carefully. I have not seen many straight 208 V three-phase, three-wire systems.

 

[waross]

For a 208 volt motor, you would run three hot circuit conductors and a grounding conductor.
For a 120/208 volt load that requires a neutral, you would run three hot circuit conductors, a neutral conductor, and a grounding conductor.
Beware the term, grounded conductor. The term may apply to a grounding conductor or a neutral conductor.
The term grounded circuit conductor generally refers to the neutral.

Bill
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